Propeller control anticipator



Nov. 17, 1959 T. P. FARKAs PROPELLER CONTROL ANTIGIPATOR Filed Oct. 1, 1956 l zi ofcem P/TcH #flu/6 POW R /NvE/vToR THOMAS 9 FAIP/(As y xfa/u); M

ATTORNEY POWER EI/Ele United States Patent O PROPELLER CONTROL ANTICIPATOR Thomas P. Farkas, Bloomield, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., `a corporation of Delaware Application October 1, 1956, Serial No. 613,106

3 Claims. (Cl. 170-135.74)

This invention relates to a propeller control and particularly to throttle actuated means temporarily controlling propeller pitch in anticipation of a change in engine power. l An object of the invention is a simple electrical mechanism for temporarily disabling a hydraulic governor for a hydraulically actuated propeller and directing uid at a predetermined rate to said propeller.

A further object is throttle actuated electronic mechanism temporarily closing a switch to actuate a valve and force the propeller pilot valve to one extreme of its movement for controlling the flow of iiuid to a hydraulic propeller pitch changing mechanism.

A still further object is an electronic device utilizing the potential of a portion of an R.C. circuit, the potential across which is being changed, as the timing mechanism for temporarily actuating a governor disabling and uid controlling switch. A still further object is mechanism including an R.C. circuit utilizing a changing potential produced by a throttle actuated potentiometer to provide a temporary bias on an electron tube to control the actuation of switching mechanism.

Other and further objects will be apparent from the following specification and the attached drawing in which:

The single figure shows a wiring diagram of the invention applied to a hydraulic governor controlling an hydraulically actuated controllable pitch propeller.

- In the operation of turbine driven propellers, it has been found that opening the throttle or increasing the fuel ilow to a turbine driving a speed-governor-controlled controllable-pitch propeller may result in an increase in turbine speed which will reach such proportions before the governor is able to sense the speed change and produce sutlicient blade chang..` to start a turbine speed reduction, that the turbine may reach dangerous overspeed conditions. duced by the governor is proportional to the speed error so that small speed changes will produce only a small rate of pitch change.

In order to avoid this overspeeding upon the opening of the throttle, applicant has devised an anticipating mechanism actuated by the turbine throttle movement which will start an increase in propeller pitch upon opening movements of the throttle without waiting for a sufcient change in turbine speed to affect the governor and increase the propeller pitch. The anticipating mechanism is used to temporarily disable the governor and at the same time supply fluid to the propeller pitch changing mechanism at a predetermined rate so that the propeller pitch is increased an amount determined by the rate and the duration of the throttle opening movement.

The anticipating mechanism is shown as applied to a governor of the type shown in Anderson Patent 2,653,668, and Farkas application Ser. No. 314,593, filed October 14, 1952, now U.S. Patent 2,840,169 applied to a propeller of the type as shown in Forman Patent Furthermore, the rate of pitch change inl ice 2,477,868 to which reference may be made for further details of the governor and propeller.

In the structure selected for illustrating the invention, a propeller shown generally at 10 having a plurality of blades, one of which is shown at 12 is driven by an engine 14 which is preferably a turbine. A hydraulic governor indicated generally at 16 is driven by gears 22, 24, 26 from the propeller shaft 18 and directs fluid to one side or the other of piston 20 to control the pitch of the blades 12. This governor is provided with a ldecrease pitch valve 28 which is electrically controlled to direct liuid from the main pump 30 to the top of pilot valve 32 to force the pilot valve downward to direct fluid from pump 30 through channel 34 to valve 32 and thence through line 36 to the inboard side of piston 20 to decrease the propeller pitch. The governor is also provided with an increase pitch valve 38 which can direct lluid from the pump 30 to the underside of pilot valve 32, thus forcing the pilot valve upward to thereby direct iluid from pump 30 to channel 34, pilot valve 32, channel 40 to the outboard side of piston 20 to increase the propeller pitch. Reference may be made to the above-identified patents and application for further details of this propeller and governor. This governor is provided with a control indicated generally at 42 by which the governor speeder spring may be set in the usual manner to select the speed at which the propeller will be governed. The governor is provided with a feathering pump shown generally at 44 which may be energized to supply pitch changing fluid when the propeller is stationary. This fluid may be directed by the decrease pitch valve and the increase pitch valve in the same manner as the fluid from pump 30 in order to change the propeller blade pitch. The engine 14 is provided with a fuel control shown generally at 46 which is controlled by means of a power lever 48.

The above-described mechanism will provide a propeller and engine combination in which the engine speed is maintained substantially constant by the governor controlied propeller in positive pitch positions and the fuel control may be varied to increase or decrease the engine po\ er.

Attached to the power lever 48 for movement therewith, is the wiper 50 of the potentiometer 52 connected across a fixed source of voltage 54 in such a way that movement of the power lever 48 to increase the power will provide a more positive voltage in the wiper arm 50. Wiper arm 50 is connected by means of a condenser 56, a resistor 58 and a biasing voltage 60 with ground and thus completing the circuit through the potentiometer back. to the source of potential 54. A resistor 62 connects the junction 64 between condenser 56 and resistor 58 with the grid of a triode 66. The plate circuit of the triode 66 energizes a solenoid 68 to actuate a pair of switches 70, 72 when the grid of the tube 66 is provided with suicient positive potential to render the tube conductive. Closing of the switch 70 will complete a circuit from the potential source 54 through line 74 to the increase pitch valve solenoid 76 to move the valve toward the left as viewed in the figure to conduct fluid from the pressure line 34 from the pump 30 to line 80 to valve chamber of valve 38 and line 82 to the underside of valve 32. Introduction of the pressure uid under the pilot valve 32 will overcome the eiect of the governor ilyweights S4, thus disabling the governor and lifting the valve 32 to a predetermined position and connect pressure line 34 with the line 40 leading to the front side of the piston 20 to move the pitch changing piston and increase the propeller pitch. The rate at which the propeller pitch can increase is determined by the capacity of the pump 30, and the size of the line to which the uid is pumped.

VInv moving the increase power lever 48 in an increase power direction, the wiper 50 is moved towards a more positive side of the potentiometer 52 to thus give a more positive potential across the condenser 56 and resistor 58 combination. The negative potentialti' in this circuit is provided tov give a normally negativevoltage on the grid of tube 66. Upon a rapid increase in thepositivel potential across condenser 56 and resistor 518the potential at junction 64 will at iirst materially increase andturn positive while the condenser 56 is charging. When the junction 64 becomes positive and consequently renders lthe potential at the grid of tube 66 positive, tube 66 will thencconduct to( energize solenoidv `68. After the potentiometer wiper 50 has been brought to rest or has materially slowed down, the voltage at junction 64 willbecome less positive as the condenser 56 becomes charged and thejunction 64 will then become negative and eventually cut oft conduction in the tube 66 and stop thei'owof current through solenoid 68 to thus permit spring v86 to open switch 70. Opening of, switch 70 will de-energize the increase pitch solenoid 76,'- connecting the underside of the pilot valve32 through line 88 to drain, thus restoring control of the pilot valve 32 to thetgovernor flyweights 84. Y

From the above description, it will be seen that movementcot` the increase power lever 48 toward an increase power'rposition at a sullciently fast rate will change the potential at junction 64 and the grid of tube 66 sufciently to disable the governor and cause an increase in propeller pitch at a predetermined rate determined by the pump capacity and the restrictions of the line connecting'the pump with the pitch changing mechanism. This governor disabling actionris a temporary phenomenon and lasts only while the condenser 56 is being charged to a dilerent potential. The size of the condenser S6 and resistor 5S is chosen to give a time constant which will provide an increase in pitch of the propeller sutlicient to absorb substantially all of the increase in power incident to movementuof the power lever 48 to an yincreased power position so that substantially no increase inthe turbine or erginespeeds will take place and control will be returned to the constant speed governor with the propeller pitch in an increased pitchl position which is substantially the correct position to absorb the entire power of the turbine being delivered to the propeller without any material speed change. Y,

This anticipating action will prevent or materially reduce any overspeeding of the turbine upon an increase in power incident to waiting f or a speed change to affect the governorbefore the governor in turn can increase the propeller pitch sufficient to! absorb the additional power and'return the turbine to the selected speed.

Movement of the power lever 48 in a decrease power direction will move the potentiometer wiper 50 to reduce the potential across the condenser S6 and resistor 58 and lthus tend to make thc junction 64' more negative. Makingy the grid of the ytube 66 more negative will, of course, have no effect except to put the tube 66 further into cut-oit so that the propeller will remain under governor controlV while the power and pitch are being reduced. Any nnderspeeding that might occur while waiting for theY governor to respond to an underspeed to reduce the propeller pitch, would not be serious.

If desired, a pilot light actuated by switch 72 can be used to advise the pilot when the governor is disabled.

Control switches 88 andV 90 have been shown for manually controlling the propeller, but other means described in more detail in the above-mentioned patents and application may be used for controlling the propeller in other regimes of operation. v

Although only one embodiment has been shown and described herein, it will be apparent that various changes and modications may be made in the construction and arrangement of the various parts without departing from the scope of this novel concept.

What is desired to be obtained by Letters Patent is:

1. A control for an engine driven propeller comprising a speed responsive governor controllingfthe propeller pitch, a` power' lever controlling engine fuel ow, means actuated by said lever including? a potentiometer connec'te'd across a source of D C. voltage, a condenser and resistor connected in vseries and with the potentiometer wiper so as to provide a voltage across said series condenser and resisterV in accordance with lever position, and provide a voltageat the iunction of said condenser and resistor varying withv the rate of movement of said power lever, and'cmea'ns, responsiveito a voltage above a preselected amount at said junction, incident to the Vrate of movement of said powerV lever, operatively connected with and temporarily disabling said governorand changing the propellerpitch.y y

2. A control as claimed in claim l in'whicli said volt- Vageresponsivemeans includes an'electron tube and means connecting the grid of s'aid'tub' with said junction; said source, potentiometer, resistor andtube arranged so that movement of said lever to increase engine power ai;V or above a predeterminedY rate will activate said tube to activate said governor disabling'and pitch changing means to 'disable said governor andl increase` the propeller pitclras long as said movement is ator above said rate.

3. Mechanism as claimedrin claim 1 in'which'the governor is a contrifugal governor having avalve actuated by ilyweig'hts and controlling the'ow of operatinglilnid to and from the propeller pitch actuating mechanismand saidl governor disabling andwpitc'h increasingmeans includesa magnetically actuated valve for, when energized, directing fluid to a motor connected with said governor valve to move said valve to an extremenpositicn and direct iui'dV to said pitch actuating mechanism to increase the propellerl pitch.

References c1466 in the 61e of" this patent UNITED s'rArEs PATENTS 1,980,146 ving'crh'oets -Nov. 6, 1934 1,985,051 Minkier Dec. 1s, 1934 2,499,813v Brady Mar. 7, o 2,628,684 slaner' Feb. 17, 1953 2,632,996 Rood Mar. 31', 1953 2,840,169 Farkas' June 24, 195s 

